Craniotomy is a fundamental technique of a neurosurgical operation and there can be listed, e.g., intracerebral hemorrhage and subarachnoid hemorrhage as a disease for which craniotomy is carried out.
A brain is made up of very soft tissue, and if a pressure in a degree of 200 mm H2O (1.96×103 Pa) is applied, it will be destroyed. For this reason, in the case of cerebral hemorrhage, 25% of the brain dies within six hours after the onset thereof, and in the case of subarachnoid hemorrhage, 35% of the brain dies within 8 hours after the onset thereof. Therefore, the therapy thereof is very urgent.
Conventionally, in order to carry out craniotomy, as shown in FIG. 3, scalp S is first incised in an arc shape to exfoliate the incised skin flap and fascia and aponeurosis under the skin flap so that cranial bone BS is exposed, and then some small holes (burr holes) H are formed with a perforator which is a drill constructed for perforating cranial bone, and a bone piece is cut using an instrument (bone saw), which is a sort of an electromotive coping saw, along a dashed line D in the figure in a manner such that these holes are connected, and the bone piece is cut away from the cranial bone using a chisel or the like if necessary so as to form a bony window. It takes usually about 10 to 15 minutes to form such a bony window.
In this craniotomy operation, since the craniotomy is carried out using a mechanical instrument such as a drill, it is necessary to strongly fix a patient's head by exclusive braces. Moreover, the cranial bone is in a state of being very slippery with patient's body fluid such as blood, and yet in order not to wound other tissues (especially brain), it is necessary to perform an operation with the utmost caution.
And after craniotomy, a dura mater is incised to take an appropriate treatment according to a disease. That is, in the case of cerebral hemorrhage, an intracerebral hematoma is removed under a microscope, or in the case of subarachnoid hemorrhage, a metallic clip is placed over a root of cerebral aneurysm.
In order to close a bony window after a treatment to a brain, since a chipping allowance becomes large and a bone piece becomes small even if the removed bone piece is damaged slightly, there is a defection that a big crevice will arise between a bone flap and a cranial bone, therefore the bone piece will fall into the crevice. For this reason, the bone piece and the cranial bone are firmly fixed using a fastener formed in a plate made of expensive titanium, and the holes formed by a drill are also covered with a metal lid. However, since the bone piece is cut out using a chisel or the like, it is difficult to cut out the bone piece without damaging the bone piece. In the case where the damage of the cut-out bone piece is severe, it cannot be used as it is, and therefore bones of a pig, a cow, or the like are used as a substitute in many cases, and there may quite likely arise a rejection to these foreign matters.
Therefore, the conventional craniotomy is a highly invasive technique with a large physical burden, and dangers of a postoperative infectious disease and rejection are also high for a patient, and since the craniotomy operation covering a plurality of processes has many points in which a medical practitioner cannot but depend on experiences and institutions, physical and mental burdens are large for a medical practitioner and malpractice may be easily induced.